Avoiding DCS with GF and MB settings

[mafi]

Recreational diving means you can keep unscrewing the cap slowly until you take it off (=surfacing) while you never saw a bubble.

I think that if we follow your analogy, recreational diving is not shaking the bottle so hard and long (diving deep and long) you cannot unscrew the cap at once (surface without staged deco).

As for the topic, I use 40/70 + extra stop at 3m over here at cold waters of Denmark

 

[Olariuas]

Which books are recommanded to buy ? about decompression theory etc ?

 

[rsingler]

Deco for Divers is the place to start, recognizing that opinions have changed SIGNIFICANTLY since it was written.

Then search threads here on SB with posts by @Dr Simon Mitchell , that reference meeting proceedings which you can download.

That's where I would begin this journey.

 

[taimen]

Pridmores Scuba Physiological is a good read for venturing into decompression theories. Well edited and easy to read. You won't learn many hard facts though. It is more about uncertainty and unknowns in decompression Science.

 

[Hatul]

For what it's worth I also dive with the G2 and use the Scubapro Aladin Tec3g as a backup. The latter uses a similar if not identical algorithm to the Galileo. I set the MB of the G2 at 2 and of the Aladin at 1 and I find they track fairly closely. The MB level gives you the time till a Level Stop, which is an optional deco stop that is supposed to provide extra safety from DCS. If you do need to violate the Level Stop you're not penalized but the computer jumps to the next lower MB level. I found these settings give a reasonable compromise between safety and the need to hang out at the deco stop or short NDL. Once you set or get to MB of 0 you're only given a hard deco stop which you're not supposed to violate.

 

[scubadada]

For what it's worth I also dive with the G2 and use the Scubapro Aladin Tec3g as a backup. The latter uses a similar if not identical algorithm to the Galileo. I set the MB of the G2 at 2 and of the Aladin at 1 and I find they track fairly closely. The MB level gives you the time till a Level Stop, which is an optional deco stop that is supposed to provide extra safety from DCS. If you do need to violate the Level Stop you're not penalized but the computer jumps to the next lower MB level. I found these settings give a reasonable compromise between safety and the need to hang out at the deco stop or short NDL. Once you set or get to MB of 0 you're only given a hard deco stop which you're not supposed to violate.

Do you do the MB stops or skip them and surface at G0? The Scubapro algorithm is relatively conservative, even at G0. See the link to the hyperbaric dives at ScubaLab 11 New Dive Computers Tested By ScubaLab In 2017

 

[rjack321]

Let me use smaller words for you.
DCS in a sinvle gas recreational dive setting with dives lasting less than NDL.
As opposed to dives with planned decompression, multiple gasses or overhead .

which happens, at a fairly low rate of 1 per 5,000(ish) dives maybe a little more in some places/regions/dive types a little less in others.

A 0.0002 "error" rate is hardly a refutation of decompression theory.

 

[ChuckP]

There is no such thing as recreational DCS.
Ongassing and offgassing are physical processes based on pressure differences, regardless of a dive being recreational, technical or commercial. The same laws apply. The biological part makes the straight-forward physical laws more difficult: different tissues behaving each in their own way and several of those tissues are dependent on the behaviour of other tissues. How the biological part behaves, depends on the person performing the dive, not on the type of dive.

If you want a good explanation of how gradient factors influence the gas model, watch Dr. Neal Pollock - decompression stress, and Simon Mitchell - decompression controversies. And read the book Deco for Divers.

Really short explanation:
There's quite a bit of history leading to all this, starting at the beginning of the last century. Haldane used goats to determine when bubbles formed in different tissues. During the sixties, Workman used all this data and determined for each of those tissues a maximum value of gasloading. In the nineties, Bühlmann created a gasmodel with 16 compartments, simplifying all tissues in a mathematical way (a compartment does not equal a tissue!). Each compartment has a different speed for ongassing and offgassing, and a Maximum-value of supersaturation.
So the idea was, that if you stayed below the M-value, no bubbles would form. Didn't work for everyone. New bright minds introduced the bubblemodel, which looked much better, with shorter decompression times. Didn't work for everyone either. Back to the gas model, but now with some modifications that makes the gasmodel behave a bit like a bubblemodel. Gradient Factors determine where your first stop will be and keep you away from that M-value in the original Bühlmann model.
Does this work for everyone? We don't know (yet). But science progresses, knowledge increases and several decompression specialists keep presenting new study results. Places like this board are perfect to discuss and criticize those results, sometimes in notorious ways.

I'm super busy here at work and sitting for a hour sometimes gets difficult - I just watched the Neal Pollock video, pretty interesting, very informative for me. Interesting all the factors that go into DCS or prevention of it.

I do use a G2 set at MB0, after looking at the test results, I'm more at just leaving that setting alone for the diving I do - maybe going to 1 if doing deeper dives that day.

 

[ChuckP]

Do you do the MB stops or skip them and surface at G0? The Scubapro algorithm is relatively conservative, even at G0. See the link to the hyperbaric dives at ScubaLab 11 New Dive Computers Tested By ScubaLab In 2017

I personally have done them and not done them - drift diving in a group can make it harder to do them, the other thing is you really have to pay attention as I personally don't think they stand out that much on the computer when they call for them......

 

[Hatul]

Do you do the MB stops or skip them and surface at G0? The Scubapro algorithm is relatively conservative, even at G0. See the link to the hyperbaric dives at ScubaLab 11 New Dive Computers Tested By ScubaLab In 2017

I followed the MB value, otherwise there’s not much point in setting it.